Fix missing links to SpeziValidation package

[Supereg]

Fix missing links to SpeziValidation package

♻️ Current situation & Problem

There were missing links in the current documentation. This PR resolves this issues.
Further, we resolve some weird DocC warning and add codecov token to coverage uploads.

⚙️ Release Notes

• Documentation fixes
• CodeCov token upload

📝 Code of Conduct & Contributing Guidelines

By submitting creating this pull request, you agree to follow our Code of Conduct and Contributing Guidelines:

• I agree to follow the Code of Conduct and Contributing Guidelines.

[PSchmiedmayer]

Thank you @Supereg! 🚀

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.18%. Comparing base (cb9441e) to head (1ef927e).

Additional details and impacted files

@@            Coverage Diff             @@
##            main      #57       +/-   ##
==========================================
+ Coverage   0.00%   76.18%   +76.18%     
==========================================
  Files        116      116               
  Lines       4017     4017               
==========================================
+ Hits           0     3060     +3060     
+ Misses      4017      957     -3060     

Files	Coverage Δ
...rces/SpeziAccount/AccountValue/AccountValues.swift	80.65% <ø> (+80.65%)	⬆️

... and 101 files with indirect coverage changes

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